n = int(input())
stone = input()
r = stone.count("R")
print(stone.count("W", 0, r)) n = int(input()) n int(input()) int input() input stone = input() stone input() input r = stone.count("R") r stone.count("R") stone.count stone count "R" print(stone.count("W", 0, r)) print stone.count("W", 0, r) stone.count stone count "W" 0 r r = stone.count("R") stone.count("R") r n = int(input()) int(input()) n stone = input() input() stone
n = int(input())
stone = input()
r = stone.count("R")
print(stone.count("W", 0, r))